The invention relates to knitted netting, and more particularly, to knitted netting as is used in wrapping, e.g., loads on pallets and bales of agricultural products. More particularly, the invention relates to knitted netting used in wrapping wherein the knitted netting is designed to minimize the transverse shrinkage of the netting.
In 1FIG. 1, Raschel knitted netting 10, including shuss (schuss), or “lateral” ribbons 12, and franze (longitudinal) ribbons 14, also known as franse ribbons, is shown and further described in U.S. Pat. No. 5,104,714 to Lieber et al. Because of the triangular pattern in the knitted netting, all Raschel netting becomes narrower when pulled lengthwise. For example, when wrapping a pallet with conventional Raschel netting, when the netting is stretched about 60%, the netting may change in width from 50 cm to about 25 cm. When a longitudinal force is applied to the knitted netting, the franzes become longer. The longer the franze gets, the longer the shuss must be to maintain the same netting dimensions. However, up to a certain degree of elongation, the shuss does not extend because the shuss tends to straighten rather than elongate. The straighter the shusses, the smaller the distance between franzes, and the narrower the netting becomes resulting in transverse shrinkage of the knitted netting.
Transverse shrinkage has been inherent in Raschel knitted netting for as long as machines to produce such knitted netting have existed. It is well known that conventional Raschel netting becomes narrower even while being knitted on Raschel knitting machines. For example, if 48″ Raschel knitted netting is desired, about 50″ netting is knitted because the netting becomes narrower by about 2″ between the knitting and the winding zones.
When a constant netting width is needed, the width can be regulated by changing the shuss tension in the knitting machine. The producers of knitted netting machines provide a facility on their machines to regulate the netting width, which depends on many factors including the type of material, temperature, ribbon dimensions, knitting tension, and knitting pattern. The knitting machine producers are aware that netting shrinkage is inherent in Raschel knitted netting. Such producers are also aware that increased tension on the shuss creates a narrower netting and loosened tension on the shuss prevents narrowing to some degree. Changing the shuss tension, however, is insufficient to fully overcome transverse shrinkage in knitted netting.
In the prior art is U.S. Pat. No. 4,781,291 to Van Ginhoven which is directed to an extruded netting. Van Ginhoven recognizes that a problem in Raschel knitted netting “is that it shrinks in overall width when pulled lengthwise”. (Col. 1, line 19.) Thus, Van Ginhoven appreciates that Raschel knitted netting shrinks when pulled lengthwise due to the geometric pattern of the knitted netting. Van Ginhoven addresses this problem by proposing a netting of square openings, instead of Raschel triangles, to solve the problem. By having transverse strands perpendicular to the longitudinal strands, creating rectangular openings instead of triangular, transverse shrinkage is overcome.
Accordingly, there is a need in the art for a knitted netting which does not shrink at all during the production process. Further, there is a need in the art for a knitted netting that maintains its full width during production and may also be widened to more than its full production width.